Minable phosphate is found in a number of places throughout the world, and in many of these deposits small quantities of uranium are found complexed with the phosphate values. The large phosphate deposit in central Florida, for example, contains from 0.01 to 0.02 weight percent uranium. This uranium is taken into solution when the phosphate is acidulated with mineral acid to produce wet-process phosphoric acid.
The early work on the recovery of uranium from wet-process acid is described in a publication referred to as DOW-81 and entitled "Recovery of Uranium from Industrial Phosphoric Acid by Solvent Extraction". Alkyl pyrophosphoric acid was found to be very efficient in selectively extracting uranium from phosphoric acid and several flow sheets utilizing this type of extractant are shown in U.S. Pat. No. 2,866,680. Prior processes for recovering uranium using a pyrophosphoric acid extractant include processes in which uranium is stripped from the extractant into an acidic stripping solution. It is also known to strip uranium from the extractant into an alkaline stripping solution.
It is an object of the present invention to provide an improved process for recovering tetravalent uranium from wet-process phosphoric acid using an extractant such as an alkyl pyrophosphoric acid and an acidic stripping solution.
A further object of the present invention is to provide an improved process for recovering uranium from wet-process acid in which uranium is stripped in the tetravalent state from an extractant such as an alkyl pyrophosphoric acid into an acidic stripping solution.
Still a further object of the present invention is to provide a process for recovering tetravalent uranium from wet-process phosphoric acid using an alkyl pyrophosphoric acid extractant and acidic stripping solution in which the pyrophosphoric acid esters remain dissolved in the extractant solution during stripping.
Yet a further object of the present invention is to provide a process for recovering tetravalent uranium from wet-process acid including means for handling any ferric iron which may be present in the pregnant extractant.
A still further object of the present invention is to provide a process for recovering tetravalent uranium from wet-process acid which is economical and minimizes consumption of costly reagents.